package org.apache.lucene.search.spans;

/**
 * Copyright 2004 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.IOException;

import java.util.Collection;
import java.util.ArrayList;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.TermPositions;
import org.apache.lucene.util.ToStringUtils;

/** Matches spans containing a term. */
public class SpanTermQuery extends SpanQuery {
    private Term term;

    /** Construct a SpanTermQuery matching the named term's spans. */
    public SpanTermQuery(Term term) {
        this.term = term;
    }

    /** Return the term whose spans are matched. */
    public Term getTerm() {
        return term;
    }

    public String getField() {
        return term.field();
    }

    public Collection getTerms() {
        Collection terms = new ArrayList();
        terms.add(term);
        return terms;
    }

    public String toString(String field) {
        StringBuffer buffer = new StringBuffer();
        if (term.field().equals(field))
            buffer.append(term.text());
        else
            buffer.append(term.toString());
        buffer.append(ToStringUtils.boost(getBoost()));
        return buffer.toString();
    }

    /** Returns true iff <code>o</code> is equal to this. */
    public boolean equals(Object o) {
        if (!(o instanceof SpanTermQuery))
            return false;
        SpanTermQuery other = (SpanTermQuery) o;
        return (this.getBoost() == other.getBoost()) && this.term.equals(other.term);
    }

    /** Returns a hash code value for this object.*/
    public int hashCode() {
        return Float.floatToIntBits(getBoost()) ^ term.hashCode() ^ 0xD23FE494;
    }

    public Spans getSpans(final IndexReader reader) throws IOException {
        return new Spans() {
            private TermPositions positions = reader.termPositions(term);

            private int doc = -1;
            private int freq;
            private int count;
            private int position;

            public boolean next() throws IOException {
                if (count == freq) {
                    if (!positions.next()) {
                        doc = Integer.MAX_VALUE;
                        return false;
                    }
                    doc = positions.doc();
                    freq = positions.freq();
                    count = 0;
                }
                position = positions.nextPosition();
                count++;
                return true;
            }

            public boolean skipTo(int target) throws IOException {
                // are we already at the correct position?
                if (doc >= target) {
                    return true;
                }

                if (!positions.skipTo(target)) {
                    doc = Integer.MAX_VALUE;
                    return false;
                }

                doc = positions.doc();
                freq = positions.freq();
                count = 0;

                position = positions.nextPosition();
                count++;

                return true;
            }

            public int doc() {
                return doc;
            }

            public int start() {
                return position;
            }

            public int end() {
                return position + 1;
            }

            public String toString() {
                return "spans(" + SpanTermQuery.this.toString() + ")@" + (doc == -1 ? "START" : (doc == Integer.MAX_VALUE) ? "END" : doc + "-" + position);
            }

        };
    }

}
